supplementary materials

Creatinium perchlorate

The title compound, C4H8N3O+·ClO4-, is built up from creatininium cations and perchlorate anions. Crystal cohesion and perchlorate stability are ensured by N-HO hydrogen bonds that together with weak C-HO interactions build up a three-dimensional network.

Studies of organic-inorganic hybrid materials, including amino acids and
various inorganic acids (Benali-Cherif et al., 2004), have
received a
great deal of attention in recent years, because of their electrical, magnetic
and optical properties (Kagan et al., 1999; Hill, 1998).

Creatinine is formed by the metabolism of phosphocreatine, a high-energy
molecule which provides a rapid supply of ATP to muscles. Phosphocreatine is
converted spontaneously to creatinine on a regular basis. Consequently,
creatinine is released into the blood and excreted by the kidneys as a
metabolic waste product.

The present structure analysis of creatininium perchlorate, (I), was undertaken
as part of a more general investigation into the nature of hydrogen bonding
between organic bases or amino acids and inorganic acids in their crystalline
forms (Cherouana et al., 2003).

In the present study, only the imino group of the imidazolyl moiety (atom N1)
in creatinine is protonated, which confirms the possibility of the existence
of creatininium cations in various tautomeric forms in aqueous solution. This
is discussed and quantified in the light of the interpretation of the solution
acidity effect on 1H, 13 C and 14 N NMR chemical shifts (Kotsyubynskyy et
al., 2004).

The asymmetric unit of (I) contains a monoprotonated creatininium cation and
two perchlorate anions (Fig.1).

The bond distances in the imidazolyl ring of (I) are, in general, not
significantly different from those found in similar hybrid compounds
containing protonated imidazolyl moieties like creatininium nitrate
(Berrah et al., 2005). The
creatininium ring is planar, as expected, with a mean deviation from planarity
of 0.0017 Å.

The average Cl—O bond distances and O—Cl—O bond angles are 1.40625 (4) Å
and 109.50 (3)°, respectively, confirming a tetrahedral configuration, similar
to other perchlorates studied at low temperature. Perchlorate anions
(ClO4-), surrounded by two creatininium residues via hydrogen bonds
play an important role in stabilizing the crystal structure.

The cation-anion N—H—O interactions form sheet parallel to the (0 1 0)
plane (Table 1, Fig.2). Weak C-H···O interactions further link the sheets to
form a three dimensionnal network (Table 1).

The title compound crystallizes in the centrosymmetric space group
P21/n. All non-H atoms were refined with anisotropic atomic
displacement parameters. All H-atoms of the cation entities were located in
difference Fourier syntheses and refined as riding model with C—H and N—H
bond lengths constrained to 0.96–0.97 Å and 0.834 Å, respectively.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger.